AB1160 SOFT TISSUE EDEMA VISUALIZED ON MUSCULOSKELETAL ULTRASOUND AS A DIAGNOSTIC TEST FOR PSORIATIC ARTHRITIS: A PILOT COHORT STUDY
Authors: T. Swami, S. Acikgoz, U. Gazel, C. Ivory, R. Chowdhury, A. Zahrai, S. Aydin, E. Hepworth
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Musculoskeletal ultrasound (MSKUS) is more sensitive than physical examination to detect inflammation in extra-articular structures in psoriatic arthritis (PsA).<sup>[1]</sup> Peritendinous soft tissue edema on MSKUS has shown to be more frequent in PsA when compared to rheumatoid arthritis (RA).<sup>[1,2,3]</sup> <h3>Objectives</h3> Here we assess the degree of association between the presence of flexor compartment (FC) soft tissue edema and the diagnosis of PsA with the aim of developing a soft tissue score to differentiate PsA from rheumatoid arthritis (RA). <h3>Methods</h3> This pilot prospective cohort study included 16 PsA and 40 RA patients from the Biologics Clinic at a single centre site in Ottawa. Patients are referred to the biologics clinic if they require initiation of, or changes to their biologic disease modifying antirheumatic drug (bDMARD). In addition to demographic and clinical data, eight MSKUS images were collected from each patient including one Grayscale (GS) and one power Doppler (PD) image of the FC of the 2<sup>nd</sup> and 3<sup>rd</sup> bilateral digits using a GE LogicE9 and a linear 15 MHz probe. Images were scored on a 0-2 semiquantitative scale to assess the degree of soft tissue edema, where 0 indicates absent, 1 indicates mild, and 2 indicates severe GS or PD. Following data collection, scoring was completed by two investigators blinded to the patients' diagnosis and in random order. Consensus decision was taken as the final score. <h3>Results</h3> Disease characteristics are provided in table 1. On MSKUS, PsA patients had a statistically significant higher total GS score compared to RA (7.0 vs 5.0, p=0.005). We found that numerically higher number of PsA patients had PD score of 2 in ≥3 fingers (20.0% PsA vs 2.5% RA, p=0.057) and GS score of 2 in ≥3 fingers (43.8% PsA and 22.5% RA, p=0.189). [Table 1] <h3>Conclusion</h3> Our results suggest a possible role for FC soft tissue edema visualized on MSKUS in both GS and PD modes to differentiate PsA from RA. It is also important to understand the impact of soft tissue edema on disease pathogenesis and patient reported outcomes. While our sample size is small, some of the tests reaching reaching statistical significance using non-parametric testing encourages us to repeat this analysis again in the future as our cohort grows. When our sample size allows, we will assess for confounding effect of seropositivity, sex, age, BMI, previous therapy, and disease duration. <h3>References</h3> [1]Tinazzi I, McGonagle D, Zabotti A, Chessa D, Marchetta A, Macchioni P. Comprehensive evaluation of finger flexor tendon entheseal soft tissue and bone changes by ultrasound can differentiate psoriatic arthritis and rheumatoid arthritis. Clin Exp Rheumatol. 2018;36(5):785-790. [2]Fassio A, Matzneller P, Idolazzi L. Recent Advances in Imaging for Diagnosis, Monitoring, and Prognosis of Psoriatic Arthritis. Front Med (Lausanne). 2020 Oct 29;7:551684. doi: 10.3389/fmed.2020.551684. PMID: 33195301; PMCID: PMC7658536. [3]Zabotti A, Salvin S, Quartuccio L, De Vita S. Differentiation between early rheumatoid and early psoriatic arthritis by the ultrasonographic study of the synovio-entheseal complex of the small joints of the hands. Clin Exp Rheumatol. 2016;34(3):459-465. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.